Sodium lauryl sulfate (SLS) in dentifrices is known to cause adverse reactions to oral tissue as shown in R. C. Caldwell and R. E. Stallard, A Textbook of Preventive Dentistry, 196, W. B. Saunders (1977); L. J. Guarnieri, IADR, Abstract No. 661 (1974); and L. J. Guarnieri, Thesis, University of Indiana (1970). One example is gingival irritation. It is also believed that SLS is responsive for sloughing of the oral mucosa. In addition, SLS is responsible for an adverse effect on taste buds causing certain foods to have a bitter taste. Furthermore, the SLS itself, in the dentifrice tastes bitter.
U.S. Pat. No. 2,812,284 shows that the soaps and synthetic detergents in dentifrices cause a harsh and/or bitter taste, which patentee has overcome by using a mixture of two specific groups of anionic surfactants, i.e., the sulfonate salts of monoglycerides of C.sub.10 -C.sub.18 fatty acids and the sulfate salts of C.sub.10 -C.sub.18 fatty alcohols, in a 3:1 ratio respectively. However, the problem of oral irritation due to the presence of anionic surfactants in the dentifrice is not mentioned in aforesaid patent.
Likewise, the use of proteins in oral preparations for sundry purposes is shown in U.S. Pat. No. 1,470,794 wherein casein, gelatin and the like is present in the dentifrice as a means of retarding the rate of the production of carbonic acid. U.S. Pat. No. 2,154,168 discloses an edible dentifrice containing casein or other animal or vegetable protein adhesive carrier as a means of buffering the pH of the composition to prevent accumulations of tooth-destroying acids. U.S. Pat. No. 4,154,813 utilizes peptides as the pH adjusting means in order to combat caries which occurs at low pH. U.S. Pat. No. 4,165,368 uses galatin as a viscosity modifier to improve the flowability of the toothpaste. However, none of aforesaid patent compositions contain an anionic surfactant, nor recognize the problems of oral tissue irritation and the bitter taste associated with the presence of said anionic surfactant.
Oral compositions containing both anionic surfactants and proteins are also well known in the art as disclosed in U.S. Pat. No. 3,925,957, wherein gelatin is used as a corrosion inhibitor. In U.S. Pat. No. 3,628,974, a water insoluble partial salt of collagen is used in the formation of a stable gel for use in cosmetics containing anionic surfactants. U.S. Pat. Nos. 4,058,595 and 4,058,596 disclose stable enzymatic toothpastes containing a neutral protease and a partially hydrolyzed protein, plus anionic or nonionic surfactant.
The purposes of the proteins in the above cited patents are to impart viscosity, provide enzymatic activity, inihibit corrosion, maintain a high pH in the dentifrice, or retard the rate of development of carbonic acid. None of said proteins are reported to counter the irritation to oral mucosa caused by anionic surfactants such as sodium lauryl sulfate.
However, none of the above cited art discloses a substantially non-irritating dentifrice composition comprising an anionic surfactant and a minor amount of a water soluble hydrolyzed protein fraction rich in positively charged amino acids or a quaternized hydrolyzed protein, having an isoionic point greater than 7 and a Bloom gel value of zero.